fix(kimi,mcp): Moonshot schema sanitizer + MCP schema robustness (#14805)

Fixes a broader class of 'tools.function.parameters is not a valid
moonshot flavored json schema' errors on Nous / OpenRouter aggregators
routing to moonshotai/kimi-k2.6 with MCP tools loaded.

## Moonshot sanitizer (agent/moonshot_schema.py, new)

Model-name-routed (not base-URL-routed) so Nous / OpenRouter users are
covered alongside api.moonshot.ai.  Applied in
ChatCompletionsTransport.build_kwargs when is_moonshot_model(model).

Two repairs:
1. Fill missing 'type' on every property / items / anyOf-child schema
   node (structural walk — only schema-position dicts are touched, not
   container maps like properties/$defs).
2. Strip 'type' at anyOf parents; Moonshot rejects it.

## MCP normalizer hardened (tools/mcp_tool.py)

Draft-07 $ref rewrite from PR #14802 now also does:
- coerce missing / null 'type' on object-shaped nodes (salvages #4897)
- prune 'required' arrays to names that exist in 'properties'
  (salvages #4651; Gemini 400s on dangling required)
- apply recursively, not just top-level

These repairs are provider-agnostic so the same MCP schema is valid on
OpenAI, Anthropic, Gemini, and Moonshot in one pass.

## Crash fix: safe getattr for Tool.inputSchema

_convert_mcp_schema now uses getattr(t, 'inputSchema', None) so MCP
servers whose Tool objects omit the attribute entirely no longer abort
registration (salvages #3882).

## Validation

- tests/agent/test_moonshot_schema.py: 27 new tests (model detection,
  missing-type fill, anyOf-parent strip, non-mutation, real-world MCP
  shape)
- tests/tools/test_mcp_tool.py: 7 new tests (missing / null type,
  required pruning, nested repair, safe getattr)
- tests/agent/transports/test_chat_completions.py: 2 new integration
  tests (Moonshot route sanitizes, non-Moonshot route doesn't)
- Targeted suite: 49 passed
- E2E via execute_code with a realistic MCP tool carrying all three
  Moonshot rejection modes + dangling required + draft-07 refs:
  sanitizer produces a schema valid on Moonshot and Gemini

tests/agent/test_moonshot_schema.py

@@ -0,0 +1,254 @@
+"""Tests for Moonshot/Kimi flavored-JSON-Schema sanitizer.
+
+Moonshot's tool-parameter validator rejects several shapes that the rest of
+the JSON Schema ecosystem accepts:
+
+1. Properties without ``type`` — Moonshot requires ``type`` on every node.
+2. ``type`` at the parent of ``anyOf`` — Moonshot requires it only inside
+   ``anyOf`` children.
+
+These tests cover the repairs applied by ``agent/moonshot_schema.py``.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from agent.moonshot_schema import (
+    is_moonshot_model,
+    sanitize_moonshot_tool_parameters,
+    sanitize_moonshot_tools,
+)
+
+
+class TestMoonshotModelDetection:
+    """is_moonshot_model() must match across aggregator prefixes."""
+
+    @pytest.mark.parametrize(
+        "model",
+        [
+            "kimi-k2.6",
+            "kimi-k2-thinking",
+            "moonshotai/Kimi-K2.6",
+            "moonshotai/kimi-k2.6",
+            "nous/moonshotai/kimi-k2.6",
+            "openrouter/moonshotai/kimi-k2-thinking",
+            "MOONSHOTAI/KIMI-K2.6",
+        ],
+    )
+    def test_positive_matches(self, model):
+        assert is_moonshot_model(model) is True
+
+    @pytest.mark.parametrize(
+        "model",
+        [
+            "",
+            None,
+            "anthropic/claude-sonnet-4.6",
+            "openai/gpt-5.4",
+            "google/gemini-3-flash-preview",
+            "deepseek-chat",
+        ],
+    )
+    def test_negative_matches(self, model):
+        assert is_moonshot_model(model) is False
+
+
+class TestMissingTypeFilled:
+    """Rule 1: every property must carry a type."""
+
+    def test_property_without_type_gets_string(self):
+        params = {
+            "type": "object",
+            "properties": {"query": {"description": "a bare property"}},
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        assert out["properties"]["query"]["type"] == "string"
+
+    def test_property_with_enum_infers_type_from_first_value(self):
+        params = {
+            "type": "object",
+            "properties": {"flag": {"enum": [True, False]}},
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        assert out["properties"]["flag"]["type"] == "boolean"
+
+    def test_nested_properties_are_repaired(self):
+        params = {
+            "type": "object",
+            "properties": {
+                "filter": {
+                    "type": "object",
+                    "properties": {
+                        "field": {"description": "no type"},
+                    },
+                },
+            },
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        assert out["properties"]["filter"]["properties"]["field"]["type"] == "string"
+
+    def test_array_items_without_type_get_repaired(self):
+        params = {
+            "type": "object",
+            "properties": {
+                "tags": {
+                    "type": "array",
+                    "items": {"description": "tag entry"},
+                },
+            },
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        assert out["properties"]["tags"]["items"]["type"] == "string"
+
+    def test_ref_node_is_not_given_synthetic_type(self):
+        """$ref nodes should NOT get a synthetic type — the referenced
+        definition supplies it, and Moonshot would reject the conflict."""
+        params = {
+            "type": "object",
+            "properties": {"payload": {"$ref": "#/$defs/Payload"}},
+            "$defs": {"Payload": {"type": "object", "properties": {}}},
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        assert "type" not in out["properties"]["payload"]
+        assert out["properties"]["payload"]["$ref"] == "#/$defs/Payload"
+
+
+class TestAnyOfParentType:
+    """Rule 2: type must not appear at the anyOf parent level."""
+
+    def test_parent_type_stripped_when_anyof_present(self):
+        params = {
+            "type": "object",
+            "properties": {
+                "from_format": {
+                    "type": "string",
+                    "anyOf": [
+                        {"type": "string"},
+                        {"type": "null"},
+                    ],
+                },
+            },
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        from_format = out["properties"]["from_format"]
+        assert "type" not in from_format
+        assert "anyOf" in from_format
+
+    def test_anyof_children_missing_type_get_filled(self):
+        params = {
+            "type": "object",
+            "properties": {
+                "value": {
+                    "anyOf": [
+                        {"type": "string"},
+                        {"description": "A typeless option"},
+                    ],
+                },
+            },
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        children = out["properties"]["value"]["anyOf"]
+        assert children[0]["type"] == "string"
+        assert "type" in children[1]
+
+
+class TestTopLevelGuarantees:
+    """The returned top-level schema is always a well-formed object."""
+
+    def test_non_dict_input_returns_empty_object(self):
+        assert sanitize_moonshot_tool_parameters(None) == {"type": "object", "properties": {}}
+        assert sanitize_moonshot_tool_parameters("garbage") == {"type": "object", "properties": {}}
+        assert sanitize_moonshot_tool_parameters([]) == {"type": "object", "properties": {}}
+
+    def test_non_object_top_level_coerced(self):
+        params = {"type": "string"}
+        out = sanitize_moonshot_tool_parameters(params)
+        assert out["type"] == "object"
+        assert "properties" in out
+
+    def test_does_not_mutate_input(self):
+        params = {
+            "type": "object",
+            "properties": {"q": {"description": "no type"}},
+        }
+        snapshot = {
+            "type": params["type"],
+            "properties": {"q": dict(params["properties"]["q"])},
+        }
+        sanitize_moonshot_tool_parameters(params)
+        assert params["type"] == snapshot["type"]
+        assert "type" not in params["properties"]["q"]
+
+
+class TestToolListSanitizer:
+    """sanitize_moonshot_tools() walks an OpenAI-format tool list."""
+
+    def test_applies_per_tool(self):
+        tools = [
+            {
+                "type": "function",
+                "function": {
+                    "name": "search",
+                    "description": "Search",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {"q": {"description": "query"}},
+                    },
+                },
+            },
+            {
+                "type": "function",
+                "function": {
+                    "name": "noop",
+                    "description": "Does nothing",
+                    "parameters": {"type": "object", "properties": {}},
+                },
+            },
+        ]
+        out = sanitize_moonshot_tools(tools)
+        assert out[0]["function"]["parameters"]["properties"]["q"]["type"] == "string"
+        # Second tool already clean — should be structurally equivalent
+        assert out[1]["function"]["parameters"] == {"type": "object", "properties": {}}
+
+    def test_empty_list_is_passthrough(self):
+        assert sanitize_moonshot_tools([]) == []
+        assert sanitize_moonshot_tools(None) is None
+
+    def test_skips_malformed_entries(self):
+        """Entries without a function dict are passed through untouched."""
+        tools = [{"type": "function"}, {"not": "a tool"}]
+        out = sanitize_moonshot_tools(tools)
+        assert out == tools
+
+
+class TestRealWorldMCPShape:
+    """End-to-end: a realistic MCP-style schema that used to 400 on Moonshot."""
+
+    def test_combined_rewrites(self):
+        # Shape: missing type on a property, anyOf with parent type, array
+        # items without type — all in one tool.
+        params = {
+            "type": "object",
+            "properties": {
+                "query": {"description": "search text"},
+                "filter": {
+                    "type": "string",
+                    "anyOf": [
+                        {"type": "string"},
+                        {"type": "null"},
+                    ],
+                },
+                "tags": {
+                    "type": "array",
+                    "items": {"description": "tag"},
+                },
+            },
+            "required": ["query"],
+        }
+        out = sanitize_moonshot_tool_parameters(params)
+        assert out["properties"]["query"]["type"] == "string"
+        assert "type" not in out["properties"]["filter"]
+        assert out["properties"]["filter"]["anyOf"][0]["type"] == "string"
+        assert out["properties"]["tags"]["items"]["type"] == "string"
+        assert out["required"] == ["query"]

tests/agent/transports/test_chat_completions.py

@@ -238,6 +238,56 @@ class TestChatCompletionsKimi:
         )
         assert kw["extra_body"]["thinking"] == {"type": "disabled"}
 
+    def test_moonshot_tool_schemas_are_sanitized_by_model_name(self, transport):
+        """Aggregator routes (Nous, OpenRouter) hit Moonshot by model name, not base URL."""
+        tools = [
+            {
+                "type": "function",
+                "function": {
+                    "name": "search",
+                    "description": "Search",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {
+                            "q": {"description": "query"},  # missing type
+                        },
+                    },
+                },
+            },
+        ]
+        kw = transport.build_kwargs(
+            model="moonshotai/kimi-k2.6",
+            messages=[{"role": "user", "content": "Hi"}],
+            tools=tools,
+            max_tokens_param_fn=lambda n: {"max_tokens": n},
+        )
+        assert kw["tools"][0]["function"]["parameters"]["properties"]["q"]["type"] == "string"
+
+    def test_non_moonshot_tools_are_not_mutated(self, transport):
+        """Other models don't go through the Moonshot sanitizer."""
+        original_params = {
+            "type": "object",
+            "properties": {"q": {"description": "query"}},  # missing type
+        }
+        tools = [
+            {
+                "type": "function",
+                "function": {
+                    "name": "search",
+                    "description": "Search",
+                    "parameters": original_params,
+                },
+            },
+        ]
+        kw = transport.build_kwargs(
+            model="anthropic/claude-sonnet-4.6",
+            messages=[{"role": "user", "content": "Hi"}],
+            tools=tools,
+            max_tokens_param_fn=lambda n: {"max_tokens": n},
+        )
+        # The parameters dict is passed through untouched (no synthetic type)
+        assert "type" not in kw["tools"][0]["function"]["parameters"]["properties"]["q"]
+
 
 class TestChatCompletionsValidate:
 

tests/tools/test_mcp_tool.py

@@ -186,6 +186,111 @@ class TestSchemaConversion:
         assert schema["parameters"]["properties"]["items"]["items"]["$ref"] == "#/$defs/Entry"
         assert schema["parameters"]["$defs"]["Entry"]["properties"]["child"]["$ref"] == "#/$defs/Child"
 
+    def test_missing_type_on_object_is_coerced(self):
+        """Schemas that describe an object but omit ``type`` get type='object'."""
+        from tools.mcp_tool import _normalize_mcp_input_schema
+
+        schema = _normalize_mcp_input_schema({
+            "properties": {"q": {"type": "string"}},
+            "required": ["q"],
+        })
+
+        assert schema["type"] == "object"
+        assert schema["properties"]["q"]["type"] == "string"
+        assert schema["required"] == ["q"]
+
+    def test_null_type_on_object_is_coerced(self):
+        """type: None should be treated like missing type (common MCP server bug)."""
+        from tools.mcp_tool import _normalize_mcp_input_schema
+
+        schema = _normalize_mcp_input_schema({
+            "type": None,
+            "properties": {"x": {"type": "integer"}},
+        })
+
+        assert schema["type"] == "object"
+
+    def test_required_pruned_when_property_missing(self):
+        """Gemini 400s on required names that don't exist in properties."""
+        from tools.mcp_tool import _normalize_mcp_input_schema
+
+        schema = _normalize_mcp_input_schema({
+            "type": "object",
+            "properties": {"a": {"type": "string"}},
+            "required": ["a", "ghost", "phantom"],
+        })
+
+        assert schema["required"] == ["a"]
+
+    def test_required_removed_when_all_names_dangle(self):
+        from tools.mcp_tool import _normalize_mcp_input_schema
+
+        schema = _normalize_mcp_input_schema({
+            "type": "object",
+            "properties": {},
+            "required": ["ghost"],
+        })
+
+        assert "required" not in schema
+
+    def test_required_pruning_applies_recursively_inside_nested_objects(self):
+        """Nested object schemas also get required pruning."""
+        from tools.mcp_tool import _normalize_mcp_input_schema
+
+        schema = _normalize_mcp_input_schema({
+            "type": "object",
+            "properties": {
+                "filter": {
+                    "type": "object",
+                    "properties": {"field": {"type": "string"}},
+                    "required": ["field", "missing"],
+                },
+            },
+        })
+
+        assert schema["properties"]["filter"]["required"] == ["field"]
+
+    def test_object_in_array_items_gets_properties_filled(self):
+        """Array-item object schemas without properties get an empty dict."""
+        from tools.mcp_tool import _normalize_mcp_input_schema
+
+        schema = _normalize_mcp_input_schema({
+            "type": "object",
+            "properties": {
+                "items": {
+                    "type": "array",
+                    "items": {"type": "object"},
+                },
+            },
+        })
+
+        assert schema["properties"]["items"]["items"]["properties"] == {}
+
+    def test_convert_mcp_schema_survives_missing_inputschema_attribute(self):
+        """A Tool object without .inputSchema must not crash registration."""
+        import types
+
+        from tools.mcp_tool import _convert_mcp_schema
+
+        bare_tool = types.SimpleNamespace(name="probe", description="Probe")
+        schema = _convert_mcp_schema("srv", bare_tool)
+
+        assert schema["name"] == "mcp_srv_probe"
+        assert schema["parameters"] == {"type": "object", "properties": {}}
+
+    def test_convert_mcp_schema_with_none_inputschema(self):
+        """Tool with inputSchema=None produces a valid empty object schema."""
+        import types
+
+        from tools.mcp_tool import _convert_mcp_schema
+
+        # Note: _make_mcp_tool(input_schema=None) falls back to a default —
+        # build the namespace directly so .inputSchema really is None.
+        mcp_tool = types.SimpleNamespace(name="probe", description="Probe", inputSchema=None)
+        schema = _convert_mcp_schema("srv", mcp_tool)
+
+        assert schema["parameters"] == {"type": "object", "properties": {}}
+
     def test_tool_name_prefix_format(self):
         from tools.mcp_tool import _convert_mcp_schema